* Colon and colorectal cancer, kidney cancer, esophageal cancer, certain types of uterine cancer, breast cancer, stomach cancer, liver cancer, gallbladder cancer, pancreatic cancer, ovarian cancer, thyroid cancer, brain cancer, brain cancer, brain cancer2 which includes 68,000 Norwegians, shows that being overweight before the age of 40 increases the risk of certain types of cancer. For cervical cancer, the risk increases by 70 percent.
Overall, the risk of obesity-related cancers increases by 15 percent if you become overweight before the age of 40. year, research shows.
Some types of cancer have a particularly high risk. At the top of the list are uterine cancer for women (70 percent), followed by kidney cancer for men (58 percent) and colon cancer for men (29 percent).
– Research shows that weight gain in adulthood is associated with increased risk of multiple cancers, Tone Bjørge, professor at the Institute of Global Health and Social Medicine at the University of Bergen, tells VG.
She and several researchers at the University of Bergen have participated in the work on a large European study – the so-called Me-Can study.
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Large research project
Researchers have extracted data from national health surveys in Norway, Sweden and Austria. 221,274 people are included in the study. To be included in the study, participants had to complete two or more health surveys, which included weight and height measurement, during the period 1972–2014.
For the study participants, an average of ten years had elapsed between each health examination. Subjects in the study were followed up on average 18 years.
The study is a so-called cohort study. That is, a study where you follow a group of people over time and see who develops the disease. The main purpose of such a study is to identify causes of illness (see fact box).
– This is a large cohort study where we have used health surveys in Sweden, Norway and Austria and linked these to national cancer registries. All participants have had a personal ID number that has enabled us to follow them over time, explains Bjørge.
– The main message is to avoid weight gain
The difference between obesity and obesity is defined by a body mass index (BMI). BMI is a measure of weight in relation to height. Those who have a BMI value between 25-29 are considered overweight. Those with BMI over 30 fall into the "obesity" category.
The study found:
- During the follow-up period in the study, 27 881 people were diagnosed with cancer.
- 9761 (35 percent) of these were related to obesity.
- The subjects in the study who were overweight (BMI over 30) at the first and second health exams had the highest risk of obesity-related cancers, compared to those who had normal BMI at the first two measurements. The risk increased by 64 percent for men and 48 percent for women.
- In particular, the risk was high for people who developed obesity before the age of 40.
– How long a person is overweight, when a person becomes overweight and how overweight the person has proven to be of great importance, says Bjørge.
– The main message is to avoid weight gain, as it reduces the risk of cancer
– An important public health message
Bjørge explains that the relationship between obesity and cancer has been extensively investigated. The fact that obesity increases the risk of several types of cancer is known, but for every new study in the field, knowledge is brought to a higher level.
– We have not reinvented powder, and our research is in line with previous research in the field. But research has an important message about public health: Avoid big weight gain as an adult, says Bjørge.
The research report, which VG has read, states that the researchers did not have available data on ethnicity and place of birth. Everyone included in the study was weighed and measured at least twice every three years before being diagnosed with cancer.
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Professor: Solid study
Anette Hjartåker is professor of nutritional epidemiology at the University of Oslo. She has worked extensively with cohort studies, been employed by the Cancer Registry and has read the study.
– This seems very solid, here a thorough work has been done. The researchers have included a large number of people – which provides a good database. They have also received measured height and weight data, which is a sign of quality, she tells VG.
She is aware that cohort studies have some weaknesses, including that not all factors are controlled. Some things can be adjusted, but not all, that the researchers also discuss in depth in the article.
– You cannot follow up so many people for so many years through a randomized controlled trial. Therefore, cohort studies are often used when looking at a large database for a long time, says Hjartåker.
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